The present invention relates to a magnetic head which writes in or reads out data in or from a magnetic recording medium, and more particularly to a wide-write/narrow-read head which is often used for a magnetic card system or an input/output section of a computer, and to a recording/reproducing method therefor.
As this type of data recording/reproducing heads, there has been known a head comprising a combination of plural cores so that the magnetic gap for writing-in and the magnetic gap for reading-out are placed one upon the other or adjacent to each other. For instance, there has been known a wide-write/narrow-read head which has a write core, a read core and a closure core arranged in a manner so that the width of the write-in track comprising write-in (recording) magnetic gaps is larger than the width of the read-out (reproducing) magnetic gap track, and the read-out track exists within the write-in track. Such a conventional wide-write/narrow-read head is shown in FIG. 10A. A closure core 3 which is substantially formed as a letter I is sandwiched between two opposing cores 1 and 2 of the letter C shape. The closure core 3 is recessed to form a dent 3a in the shape of U at the center end thereof, and the first C-shaped core (read core) 1 is projected 1a at the center tip thereof so that the projection 1a of the read core 1 is inserted into the dent 3a of the closure core 3. The projection 1a is opposed to the tip end 2a of the second C-shaped core (write core) 2. This portion is used as a central magnetic gap (read gap) 4 while the portion where the tip end 2a of the core 2 is opposed to the closure core 3 is used as side magnetic gaps or closure gaps 5, 5. Read-out winding 6 is coiled on said read core 1 and write-in winding 7 on said write core 2. A central magnetic circuit A is defined to extend on the central portions of the read core 1 and the write core 2 as shown by solid-line-and-arrows while side magnetic circuits B are defined to pass between the write core 2 and the closure core 3 as shown by broken-line-and-arrows in the figure. Data are written in over the whole width W of the central magnetic gap 4 as well as the closure gaps 5, 5 on both sides thereof by the electric current of the write core 2. For reading out of the data, the narrower width W' of only the central magnetic gap 4 of the read core 1 is used. (Refer to FIG. 11.)
As shown in FIGS. 12A and 12B, in the prior art digital recording magnetic head of this type, the closure core 3 is not recessed so deeply to form the dent portion 3a at the front end of the core 3 in order to maintain a certain strength thereon, but is recessed in the depth only sufficient to receive the projection 1a at the center tip of the read core 1. The core width of the closure core front end opposite to the write cores on both sides of the recess 3a or, in other words the thickness T of the core in the direction of the traveling magnetic medium remains as thick as or almost similar to the length of the projection 1a of the read core 1. (Refer to FIG. 10B.)
This type of magnetic head generally writes in data in so-called "saturation recording". As magnetic circuits A and B are generated in plurality as a whole head core, and further the circuit B is divided at the front end portion of the closure core to the circuits B.sub.1 and B.sub.2 (B=B.sub.1 +B.sub.2), as shown in FIG. 10B, crosstalk will occur in the circuit A because of the influence from the side magnetic circuits B when the data is being read out. Especially in the aforementioned type, as the recess 3a formed at the front end of the closure cores 3 has a depth only sufficient to receive the projection 1a of the read core 1 as shown in FIGS. 10A, 10B, and as the read core 1 and the closure core 3 are proximal to each other in position, the side magnetic circuits B between the write core 2 and the closure core 3 come closer to the central magnetic circuit A extending from the write core 2 to the read core 1 at the front end projection thereof, increasing crosstalks on the circuit A from the closure gaps 5, 5 through said recess 3a of the closure core 3 and deteriorating the read characteristics.